The fuel cells represent known technology. They are used to convert chemically bound energy into electricity and heat, by bringing the fuel into contact with an oxidising component. The most common fuel is hydrogen, but also hydrocarbons, such as natural gas and particularly its most common derivatives (alcohols, organic acids and aldehydes or ketones), however, in most cases for instance methanol, are used. From methanol it is possible to produce electrical energy by using fuel cells, either indirectly by steam reforming, in which case methanol is first converted into hydrogen, or by directly oxidising methanol into carbon dioxide and water.
Typically, the latter reaction is carried out in the presence of a precious metal catalyst, in a “direct methanol fuel cell”. In the anode space of the direct methanol fuel cell, the methanol becomes oxidised in the presence of water, thereby forming mainly carbon dioxide (CO2), protons and electrons, and in the cathode space, the oxygen is correspondingly reduced.
Generation and removal of carbon dioxide is one of the main problems of fuel cells which are based on direct oxidation of methanol. One cause of this problem is that gaseous CO2 is generated in the fuel as a by-product, which, in turn, generates overpressure. Because direct methanol fuel cells are generally used at relatively high temperatures in order to achieve sufficient power density the CO2 that is generated must be discharged from the system, in which case substantial volumes of methanol steam are discharged at the same time.
Elimination of overpressure by flushing out the CO2 leads to a simultaneous discharge of the gasified methanol into the environment, and thereby presents a risk of substantial poisoning and also a risk of an explosion/fire.
There are other problems of the direct methanol fuel cells, such as:                low current density and thus also low power density—which means that the fuel cells are expensive when high power is needed,        without a system of feeding the fuel, the power of the fuel cell is extremely low, and        a cell equipped with a fuel feeding system has a substantially improved power density, but the feeding is based on the use of a pump, which thereby causes power losses, and malfunctions.        
Publication US2006/0115702 describes a fuel system solution which is comprised of two separate chambers. The tank is connected to a fuel cell and when the cell is operating, the water released from the cathode side is led to the other side of the fuel system. Because of this and because the amount of fuel is decreasing, a movable separating wall in the tank moves along with the water towards the fuel, which compensates for the change in volume. However, the system described in the publication does not remove the main problems associated with direct methanol fuel cells, such as the generation of CO2 and the resulting overpressure. The same applies to those known systems which are described in publications EP 1 306 917, US 2005/0130009, JP 2006252812 and JP2005032702.
Consequently, the overall situation regarding direct oxidation fuel cells remains very problematic.